Malfunction Indicator Lamp: Description and Operation

1987 Pontiac Firebird V8-350 5.7LSECTION Description and Operation

"Check Engine" Or "Service Engine Soon" Lamp (CEL)
This warning lamp, located on the instrument panel, serves two purposes: to alert the vehicle operator that a fault has been detected in the system and should be serviced as soon as possible and as a diagnostic aid to display trouble codes. The "Check Engine" Lamp (CEL) and "Service Engine Soon" lamp perform the same function and which light is used depends on particular vehicle application.

This lamp will illuminate with the ignition key on and the engine not running. When the engine is started, the lamp should go out. If the lamp remains lit, the self-diagnostic system has detected a malfunction. If the malfunction clears, the lamp will go out after ten seconds and a trouble code will be stored in the ECM.


RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.